Communication systems

The human body has two communication systems that allow us to respond to any changes in our environment.

The nervous system uses nerve impulses (electrical impulses) to react quickly to a stimulus.

The hormonal system uses hormones to react slowly to a stimulus.

Nervous systemHormonal system
SpeedFastSlow
Nature of responseElectrical impulsesHormones/chemicals that travel in blood

The nervous system

The brain and spinal cord form the central nervous system (CNS). The CNS controls and coordinates responses between receptors and effectors.

Diagram of the human central nervous system with the brain and spinal cord labelled

  • Stimuli are changes in our environment that we respond to and are detected by receptors.
  • Different receptors are sensitive to different stimuli (e.g. receptors in the eye are sensitive to light).
  • A nerve cell/neurone carries information in the form of nerve impulses from the receptor to the coordinator.
  • The coordinator – brain or spinal cord – determines whether or not to respond to the stimulus.
  • A neurone carries information from the coordinator to an effector.
  • An effector is a muscle or gland that can bring about a response.
Diagram summarising how information flows from receptors to effectors in the nervous system.